The present invention relates to a gas-shielded arc welding apparatus comprising a combination of a teaching playback robot and an arc welding power source.
Gas-shielded arc welding has mainly used a helium gas, an argon gas, a carbon dioxide gas, or a mixture of these gases as shielding gas for protecting a welded part from ambient atmosphere. Depending on the various gases, there are a metal inert gas (MIG) arc welding method, a CO2 gas shielded arc welding method (CO2 arc welding method), and a metal active gas (MAG) arc welding method. A pulsed arc welding method in which pulse current is periodically made to flow is also known.
Each arc welding method employs a welding power source appropriate to the arc welding method. When welding is performed using a combination including a teaching playback robot (hereinafter simply referred to as a robot), an adjustment for providing consistency between a robot control apparatus and an arc welding power source is required for each arc welding method. This adjusting operation is required every time the combination with the robot is changed to use another welding power source for a different welding method.
An arc welding apparatus comprises a shielding gas solenoid valve and a shielding gas supply controller in order to continuously supply the shielding gas to a shielded part for a certain period before welding, during the welding, and for a certain period after the welding. Before welding work is performed, generally, a shielding gas flow rate is adjusted to a reasonable amount for preparation of the task. A gas flow rate adjuster mounted to a gas cylinder or a gas supply pipe performs this adjustment of the shielding gas flow rate. Most of gas flow rate adjusters to be mounted to the gas cylinder have a structure integrally combined with a gas-pressure regulating valve. The gas flow rate adjuster is generally deposited away from the gas solenoid valve and a gas controller. Because the adjustment of the gas flow rate requires experimentation with the gas supply regardless of the welding, the welding apparatus includes a gas check switch used for supplying gas experimentally. The gas check switch has a function of switching between xe2x80x9csupplyxe2x80x9d and xe2x80x9cstopxe2x80x9d of the gas. However, if the switch is left set on the xe2x80x9csupplyxe2x80x9d side, the shielding gas continues to be supplied regardless of the welding.
Japanese Patent Laid Open No. 11-77309 discloses a gas-shielded arc welding apparatus including a stop mechanism of shielding gas supply for preventing undesired supply of the shielding gas during non-welding. In the technology disclosed in this Japanese Patent Laid Open, a timer starts counting time synchronously with the opening of a solenoid valve for supplying and stopping the shielding gas by operation of a gas check switch. After a time-out period set in the timer is achieved, the solenoid valve is closed to stop the shielded gas supply even if the gas check switch is left set to the supply position of the shielded gas. As a result, the disclosed apparatus has an effect of preventing expensive shielding gas from being uselessly consumed even if the gas check switch is not return to the xe2x80x9cstopxe2x80x9d side.
However, in a case of a welding power source disclosed in Japanese Patent Laid Open No. 11-77309 supplying or stopping the shielding gas is performed only by the welding power source. Thus, a problem may occur when the welding power source is used for the arc welding apparatus comprising a combination of the welding power source and a teaching playback robot without any adjustment.
For example, for adjusting a shielding gas flow rate with the shielding gas flow rate adjuster, an operator must perform the following processes:
setting a gas check switch on the welding power source to the xe2x80x9csupplyxe2x80x9d side to open a gas solenoid valve into a gas supply state;
adjusting the shielding gas flow rate to a desired value with the shielding gas flow rate adjuster at the position of the shielding gas flow rate adjuster;
returning the gas check switch to the xe2x80x9cstopxe2x80x9d side again at the position of the welding power source; and
closing the gas valve to stop the supply of the shielding gas.
The operator must troublesomely perform the adjustment before every welding.
The welding power source disclosed in the Japanese Patent Laid Open, as discussed above, is used for automatically closing the gas valve to stop the supply of the shielding gas when the timer achieves the set time-out period even if the gas check switch is forgotten about and not returned to the stop side. This function is useful as a measure to counter forgetfulness. However, this function may unfortunately allow the operator to leave the check switch as it is without noticing that he or she has forgotten to return the check switch to the xe2x80x9cstopxe2x80x9d side.
Additionally, the entire stop mechanism of shielding gas supply is hardware. When the return of the check switch is forgotten, the check switch is left set to the gas supply side while an input switch on the welding power source side is turned off and then turned on. The non-operation of the switch prohibits a trigger from starting the counting of time by the timer, which results in continuing the shielding gas supply.
In an arc welding apparatus comprising a combination of a robot-only arc welding power source and the teaching playback robot, a robot controller side dominates the control of the shielding gas supply. Therefore, when the operator, during teaching for the robot, forgets to register a shielding gas control sequence or teaches an inappropriate sequence at the start or completion of the welding, a welding defect such as a blowhole disadvantageously occurs.
It is an object of the present invention to provide an arc welding apparatus comprising a combination of a teaching-playback robot and a welding power source, considering the conventional problems discussed above. This arc welding apparatus does not require any adjustment for providing consistency between a robot controller and the arc welding power source, even when replacement of one arc welding power source for one welding method to another welding power source for another welding method is performed during changing the welding method.
The arc welding apparatus in accordance with the present invention comprises a teaching-playback robot comprising a robot body and a robot controller, and a welding power source including a controller. The robot controller and the welding power source both have an external interface, and can communicate with each other using a digital signal. Based on information on the welding method transmitted from the welding power source, the welding method is automatically set in the robot controller.
Even when the welding power source combined with the robot is replaced by the other welding power source for a different welding method, the robot controller corresponds to the latter welding power source on the basis of the information on the latter welding method sent from the latter welding power source. Therefore, an operator needs not adjust between the welding power source side and the robot controller side.